Synergistic stabilizer compositions for polyols and polyurethane foam

ABSTRACT

Polyether polyols and polyurethane foams are stabilized by including therein a liquid stabilizer composition of (a) 2,6-di-tert-butyl-4-sec-butylphenol, (b) a reaction product of diisobutylene, styrene and diphenylamine and (c) phenothiazine or C 9-26  -alkyl substituted phenothiazine and wherein the ratio of the phenol to the reaction product is about 1:5 to 5:1 and the ratio of the mixture of components (a) and (b) to the phenothiazine compound is about 5.0:0.1 to 4.0:1.0. The stabilizer composition may further contain trihydrocarbyl phosphite to stabilize the color of same.

BACKGROUND OF THE INVENTION

The present invention concerns stabilization of polyoxylakylenepolyether polyols and the use of the stabilized polyols in thepreparation of polyurethane foam. In particular the invention relates tostabilization of polyols with certain liquid stabilizer compositions andthe color or scorch inhibition of flexible and semiflexible polyurethanefoams made from the stabilized polyols.

Prior art methods for stabilization of polyoxyalkylene polyether polyolswith solid antioxidants or stabilizers and the use of the stabilizedpolyols in the preparation of polyurethane foams to inhibit scorch arewell known.

Conventional solid stabilizers are generally dissolved in the polyolmedia by heating. To remove any undissolved stabilizer solids, theentire voluminous polyol mass is subjected to a filtration step. Thenthe polyol precursor can be processed into the final foam product.

U.S. Pat. No. 4,933,374 discloses a liquid stabilizer compositioncomposed of 2,6-di-tert-butyl-4-sec-butylphenol and a reaction productof diisobutylene, styrene and diphenylamine. The liquid stabilizereliminates certain processing disadvantages associated with solidstabilizer systems. The liquid stabilizer compositions are readilysoluble in the polyol media at ambient temperatures. Consequently, twosteps of the conventional process may be eliminated: dissolution of thestabilizer in the polyol media by heating and removal of undissolvedstabilizer solids by filtration. Furthermore, the liquid stabilizercompositions may be added to the polyol by metering or pumping forconvenience and safety.

Another known scorch inhibitor is phenothiazine disclosed in U.S. Pat.No. 3,214,397. U.S. Pat. No. 4,010,211 teaches the replacement of partof a solid stabilizer system composed of butylated hydroxytoluene andp,p'-dialkyldiphenylamine with phenothiazine or its alkyl derivatives.

U.S. Pat. No. 4,275,173 discloses a solid synergistic stabilizer systemconsisting of a sterically hindered phenolic antioxidant, 4,4'-bis (α,α-dimethylbenzyl)diphenylamine and phenothiazine or its alkylderivatives.

Surprisingly, it has been discovered that phenothiazine and certainalkyl derivatives of phenothiazine can be added to the liquid stabilizercomposition composed of 2,6-di-tert-butyl-4-sec-butylphenol and areaction product of diisobutylene, styrene and diphenylamine withoutdestroying the liquid character of the stabilizer composition, whilesynergistically improving the overall scorch inhibiting properties ofthe stabilizer.

SUMMARY OF THE INVENTION

According to the invention, there are provided polyoxyalkylene polyetherpolyol compositions stabilized against oxidative degradation with astabilizing amount of a synergistic mixture of2,6-di-tert-butyl-4-sec-butylphenol, a reaction product ofdiisobutylene, styrene and diphenylamine, and phenothiazine compound ofthe formula I below, wherein the ratio of the phenol to the reactionproduct is about 1:5 to 5:1, and the ratio of the mixture of the phenoland the reaction product to the phenothiazine compound is about 5.0:0.1to 4.0:1.0.

Another aspect of the invention concerns a method for the stabilizationof a polyoxyalkylene polyether polyol against oxidative degradation andthe use of the stabilized polyol together with polyisocyanates toprepare scorch stabilized polyurethane foam, wherein the polyol containsabout 0.01 to 5.0 percent by weight of a synergistic mixture consistingof 2,6-di-tert-butyl-4-sec-butylphenol, a reaction product ofdiisobutylene, styrene and diphenylamine, and phenothiazine compound ofthe formula I ##STR1## wherein each R is independently hydrogen or analkyl group having 9 to 26 carbon atoms.

DETAILED DESCRIPTION OF THE INVENTION

The synergistic stabilizer or antiscorch composition is composed ofknown compounds. The liquid reaction product of diisobutylene, styreneand diphenylamine is prepared in the presence of a Friedel-Craftcondensation catalyst according to the method described in U.S. Pat. No.2,530,769 and is herein incorporated by reference. The weight ratio ofdiisobutylene to styrene ranges from about 2:1 to 5:1, preferably from3:1 to 4:1 and the mole ratio of the hydrocarbon mixture containingdiisobutylene and styrene to diphenylamine ranges from about 1.3:1 to2:1, preferably from 1.3:1 to 1.5:1.

The composite liquid reaction product consists of octylated andstyrenated derivatives such as p,p'-di-tert-octyldiphenylamine,p,p'-di-phenylethyldiphenylamine,p-tert-octyl-p'-phenylethyldiphenylamine, p-tert-octyldiphenylamine,p-phenylethyldiphenylamine and tri-tert-octyldiphenylamine. In addition,the product contains butylated derivatives which are produced when thetert-octyl group having the structural formula ##STR2## is split intotwo tert-butyl groups by the catalyst producing derivatives such asp-tert-butyldiphenylamine, p,p'-di-tert-butyldiphenylamine,p-tert-octyl-p'-tert-butyldiphenylamine,p-tert-butyl-p'-phenylethyldiphenylamine and minor amounts of otherunidentified reaction products.

For preparation of the stabilizer of the invention, preferred arereaction products containing about 50 to 80 percent of mixed octylatedderivatives, p-tert-octyldiphenylamine,p-tert-octyl-p'-tert-butyldiphenylamine,p,p'-di-tert-octyldiphenylamine,p-tert-octyl-p'-phenylethyldiphenylamine and tri-tert-octyldiphenylamineand about 50 to 20 percent of mixed butylated and styrenateddiphenylamine derivatives.

The second component of the stabilizer composition,2,6-di-tert-butyl-4-sec-butylphenol, is a known material availablecommercially under the trade name VANOX® 1320 (distributed by R. T.Vanderbilt Company, Inc.)

The third component of the stabilizer composition is represented byformula I hereinabove. This includes unsubstituted phenothiazine,monoalkylphenothiazine, dialkylphenothiazine and mixtures thereof. Theposition of each alkyl group on each of the two aromatic groups is notcritical. The alkyl groups represented by the radical R contains 9 to 26carbon atoms. The alkyl groups may be straight chain or branched chain.The illustrative phenothiazine compounds include dinonylphenothiazine,didodecylphenothiazine, dioctadecylphenothiazine, dieicosylphenothiazineand ditetracosylphenothiazine.

To preserve the liquid character of the stabilizer system, thephenothiazine compound is dissolved in polyol or thepolyether-isocyanate prepolymer and the desired amount of the stocksolution added to the other two ingredients.

Unexpectedly, the phenol compound, the reaction product and thephenothiazine compound produce synergistic antioxidant effect in polyolswhen combined in certain critical ratios. Synergism is displayed whenthe phenol and the reaction product is present in the ratio of 1:5 to5:1 and the mixture of the two components and the phenothiazine compoundis present in the ratio of 5:0:0.1 to 4.0:1.0.

The antioxidant composition has a tendency to discolor upon standing. Toprolong shelf-life of the composition, it is advantageous to add about0.5 to 10.00 percent of trihydrocarbyl phosphite wherein the hydrocarbylgroup may be independently selected from phenyl and alkyl groups.Preferred are alkyl derivatives having 5 to 13 carbons and higher.Particularly preferred are the compounds tridecyl phosphite and phenyldiisodecyl phosphite.

The compositions of the invention may be incorporated in the polyolprecursors in an amount effective to produce the desired stability.Typically, an amount from about 0.01 to 5.0 percent will be sufficient.A preferred range is from about 0.3 to 1.0 percent by weight of thetotal polyol composition. Because of their liquid nature, the stabilizercomposition may be incorporated into the polyol by simply stirring atambient temperatures.

The polyol components which may be stabilized with the stabilizercomposition of the invention include polyoxyalkylene polyether polyolshaving 2 to about 10 hydroxy groups. Particularly suitable polyolsinclude those having a molecular weight of about 200 to 10,000 orhigher. Preferred are polyols derived from diols and triols with amolecular weight ranging from 1000 for diols to 6000 for triols.

The polyether polyols possess two or more ether groups in the molecule.The polyols are derived from, among others, ethylene oxide, propyleneoxide, epichlorohydrin, styrene oxide, diethylene glycol, triethyleneglycol, trimethylolpropane, glycerine, hexanetriol, butanetriol and thelike. Polyether polyols suitable for preparation of flexiblepolyurethane foams and methods of their preparation are described in K.C. Frisch and J. H. Saunders, ed., PLASTIC FOAMS, Part 1, 118-125(1972).

In the preparation of flexible polyurethane foams, the stabilized polyolcompositions are reacted with a polyisocyanate containing two or more--N═C═O groups per molecule in the presence of catalysts, surfactants,water and optionally, auxiliary blowing agents. Commercially availablepolyisocyanates include, among others, toluene-(2,4 and/or2,6)diisocyanate, 4,4'-diphenylmethane diisocyanate, polyisocyanate fromaniline-formaldehyde oligomers and aliphatic isocyanates such asmethylcyclohexane diisocyanate and the like.

Because of increased safety considerations, flexible and semiflexiblepolyurethane may contain flame retardants. The latter are knowncompounds containing phosphorus, antimony, boron, bismuth and halogen orcombinations thereof. The polyurethane may contain other additives suchas fillers, plasticizers, reodorants, ultraviolet and thermalstabilizers and the like.

The data hereinbelow are intended to illustrate, but not to limit thescope of the invention. Unless otherwise stated, all parts andpercentages in the specification and claims are expressed by weight.

EXAMPLE

Scorch resistance of polyurethane foams was determined by microwavescorch test.

The specimens given in Table I were prepared by mixing the ingredientsin a high intensity mixer, pouring into 35×35×13.75 cm cardboard box andrecording the cream and rise time (health bubbles). The foamed specimenswere placed in a microwave oven at 30% power for 7.5 minutes, rotated180 degrees and microwaved for 7.5 minutes. Thereafter, the specimenswere placed in a 121° C. forced air convection oven for 2 minutes tocure skin and then allowed to cure for 30 minutes at room temperature.The peak exotherm was measured for 10 minutes with a digitalthermometer. The cured foam was cut open and discoloration wasdetermined by visual inspection.

Specimen 1 contained no stabilizer and was severely discolored. Specimen2 contained a 2.5:1 mixture of 2,6-di-tert-butyl-4-sec-butylphenol andreaction product of diisobutylene, styrene and diphenylamine (VANLUBE®SL-HP distributed by R. T. Vanderbilt Company, Inc.), hereinafter2-component stabilizer. Specimen 3 contained the same amount of thethird component, phenothiazine. Both specimens were severely discolored.Specimens 4 to 7 contained the synergistic three component mixtures ofthe invention and showed very light to moderate discoloration as aresult of improved scorch resistance.

                                      TABLE I                                     __________________________________________________________________________    COMPOSITIONS, PARTS                                                           COMPONENTS  1    2    3    4    5    6    7                                   __________________________________________________________________________    Polyether polyol.sup.1                                                                    100.00                                                                             100.00                                                                             100.00                                                                             100.00                                                                             100.00                                                                             100.00                                                                             100.00                              Distilled water                                                                           5.50 5.50 5.50 5.50 5.50 5.50 5.50                                Silicone surfactant.sup.2                                                                 1.20 1.20 1.20 1.20 1.20 1.20 1.20                                Amine catalyst.sup.3                                                                      0.47 0.47 0.47 0.47 0.47 0.47 0.47                                Flame retardant.sup.4                                                                     7.00 7.00 7.00 7.00 7.00 7.00 7.00                                Tin catalyst.sup.5                                                                        0.25 0.25 0.25 0.25 0.25 0.25 0.25                                Toluene diisocyanate                                                                      70.80                                                                              70.80                                                                              70.80                                                                              70.80                                                                              70.80                                                                              70.80                                                                              70.80                               2-Component stabilizer                                                                    --   0.5  --   0.49 0.49 0.45 0.4                                 Phenothiazine                                                                             --   --   0.5  0.01 --   0.05 0.1                                 Dinonylphenothiazine                                                                      --   --   --   --   0.01 --   --                                  Scorch      Very Severe                                                                             Severe                                                                             Very Moderate                                                                           Light                                                                              Moderate                                        Severe         Light                                              __________________________________________________________________________     .sup.1 NIAX ® 1652 manufactured by Union Carbide Company                  .sup.2 NIAX L5750 manufactured by Union Carbide Company                       .sup.3 NIAX A 127 manufactured by Union Carbide Company                       .sup.4 FYROL FR 2 manufactured by Akzo                                        .sup.5 NIAX D 19 manufactured by Union Carbide Company                   

The above embodiments and illustrations have shown various aspects ofthe present invention. Other variations will be evident to those skilledin the art and such modifications are intended to be within the scope ofthe invention as defined in the appended claims.

What is claimed is:
 1. In the preparation of polyurethane foams byreacting a polyether polyol and polyisocyanate, the improved method ofreducing discoloration due to scorch of polyurethane foams comprisingthe steps of (i) adding to the polyol about 0.01 to 5.0 percent byweight of a liquid stabilizer composition consisting of (a)2,6-di-tert-butyl-4-sec-butyl phenol, (b) a reaction product ofdiisobutylene, styrene and diphenylamine wherein the weight ratio ofdiisobutylene to styrene ranges from about 2:1 to 5:1 and the mole ratioof the mixture of diisobutylene and styrene to diphenylamine ranges fromabout 1.3:1 to 2:1 and(c) phenothiazine compound of the formula ##STR3##wherein each R is independently hydrogen or and alkyl group having 9 to26 carbon atoms and wherein the ratio of the phenol compound to thereaction product is about 1:5 to 5:1 and the ratio of the mixture ofcomponents (a) and (b) to the phenothiazine compound is about 5.0:0.1 to4.0:1.0, (ii) stirring the polyol and stabilizer mixture at ambienttemperature and (iii) curing in the presence of a reaction catalyst andfoaming agent.